Effect of mecoprop drift on some plant species of conservation interest when grown in standardized mixtures in microcosms

There has been an increasing awareness of potential impacts of herbicide drift on to vegetation in nature reserves and field margin habitats adjacent to treated areas. Previous work using single species bioassays has suggested that the effects of a single drift event are confined close to the sprayer (< 10 m). In the present study eight native dicotyledonous species, with and without a perennial grass (Lolium perenne), were grown in standardized microcosms in order to study (1) the effects of herbicide drift where plants were exposed to competition, and (2) the effects of a second spray application. The microcosms were arranged downwind (0-8 m) of a standard agricultural sprayer applying mecoprop at recommended rates. The effects of the herbicide drift on foliar symptoms of plant damage and end-of-season yield were assessed in each of two years. The main conclusions were that (1) growth of Stachys sylvatica and Lolium perenne (where sown) was enhanced near the sprayer and, (2) six other species (Digitalis purpurea, Galium mollugo, Hypericum hirsutum, Lychnis flos-cuculi, Primula veris and Ranunculus acris) showed some evidence of reduction in either performance (assessed non-destructively after a single exposure) or yield after two exposures. Three species (Lychnis flos-cuculi, Primula veris and Ranunculus acris) showed a reduction in flowering performance. Thus, mecoprop drift affected the aesthetic appearance, possibly the fecundity of some species and the balance between species in these microcosm experiments. The implications of these results for the persistence of attractive plant communities in sensitive areas are discussed.     

Size-related aspects of arm damage, tissue mechanics, and autotomy in the starfish Asterias rubens

 Arm damage is a widely reported but superficially investigated aspect of the biology of the starfish Asterias rubens L. In the present study, the incidence of arm damage was surveyed in populations of A.  rubens at two sites in the Firth of Clyde, Scotland, and three sites in Gullmarsfjorden, Sweden. The mean (±SD) incidence across all sites of individuals with basal arm damage (resulting from detachment at the basal autotomy plane) was 19.69 ± 8.86%, the incidence of those with distal arm damage (resulting from amputation at more distal levels) was 7.74 ± 10.01%. The mean incidence of arms with basal damage was 5.28 ± 4.12%, of those with distal damage 1.83 ± 2.45%. There was a significant negative correlation between size and the incidence of basal damage at all but one site, but no significant correlation between size and distal damage at any site. Mechanical tests on specimens of the aboral body wall from the basal region of the arm (which included the autotomy plane) and from a more distal region revealed that with increasing body size there was a significant increase in yield stress, ultimate stress and Young's modulus (stiffness) but no significant change in yield strain and ultimate strain. There was no significant difference between the relationships for basal and distal specimens. It is hypothesised that in larger individuals increased mechanical toughness replaces autotomy as an effective antipredator strategy. Using two methods to induce autotomy, a significant positive correlation between size and the delay between the onset of stimulation and arm detachment was found; this may represent a size-related decline in the efficiency of the autotomy mechanism through the relaxation of selection pressure. Since size is an unreliable indicator of age in A.  rubens, the trends identified herein can be interpreted only tentatively as age-associated phenomena. Received: 4 September 1999 / Accepted: 17 February 2000     

Spatial and temporal variations in sediment accumulation in an algal turf and their impact on associated fauna

Marine Biology - The relationships between the fauna inhabiting an intertidal algal turf, Osmundea pinnatifida, and the accumulated sediment were studied in the autumn and summer. The investigation...     

A Microcosm Approach to the Detection of the Effects of Herbicide Spray Drift in Plant Communities

It is often difficult to measure and predict the impacts of toxic chemicals, such as herbicides, on natural communities. This is especially true under conditions of spray drift when the amount received by the organisms downwind from the sprayer may be at sub-lethal doses. Laboratory experiments are either artificial, or have not been generally carried out over long enough time periods, to be realistic. Field experiments are often difficult because of the high variability inherent in natural populations. Here an intermediate microcosm approach was used, where standardized artificial communities (eight dicotyledons with and without a grass) were tested. The artifical communities included species typical of British woodland margins, hedgerows and field margins; communities with a high conservation interest, yet potentially under threat from spray drift. The microcosms were placed downwind of a sprayer and exposed to one of the following herbicides: glyphosate, mecoprop and MCPA. This approach ensures that the communities were standardized at the start and have been exposed to realistic doses of herbicide. The experiments reported here were carried out for at least three years with exposures to herbicides repeated each year. The effects of differential herbicide exposure downwind of the sprayer were measured on species yield, flowering performance, seed production, seed viability and invasion by new species. Responses were extremely variable, but all species showed some effects in some years. Some patterns emerged. For example, one group of species appeared to be more successful near to the sprayer. This was particularly true of the grass when exposed to MCPA and mecoprop. The performance of most species was reduced under the sprayer, and there was a general recovery with increasing distance downwind. A few species showed increased performance in the intermediate downwind zone (2–4 m) and this may be due to a hormonal effect on growth processes, or an effect of reduced interference from other community members. Generally, there were few effects on seed production or seed viability. An important result was that most effects were confined within an 8 m zone, as there were few significant differences between plants exposed at 8 m and those untreated. Although damaging effects were found in the immediate downwind zone from the sprayer, the restriction of effects to 8 m suggests that a buffer zone of this size would be adequate to protect sensitive habitats from most deleterious impacts on community processes.     

Competing conservation goals, biodiversity or ecosystem services: element losses and species recruitment in a managed moorland-bracken model system

Conservation management in Europe is often geared towards restoring semi-natural ecosystems, where the objective is to reverse succession and re-establish early-successional communities, to comply with national and international conservation targets. At the same time, it is increasingly recognised that ecosystems provide services that contribute to other, possibly conflicting policy requirements. Few attempts have been made to define these conflicts. Here, we assess some potential conflicts using a Calluna vulgaris-dominated moorland invaded by bracken (Pteridium aquilinum) as a model system, where the current policy is to reverse this process and restore moorland. We examined impacts of bracken control treatments on services (stocks and losses of C and mineral nutrients), litter turnover and biodiversity within a designed experiment over 7 years. Bracken litter was >2000 g m(-2) in untreated plots, and treatments reduced this quantity, and its element content, to varying degrees. Cutting twice per year was the most successful treatment in reducing bracken litter and its element content, increasing litter turnover, and increasing both mass and diversity of non-bracken vegetation. Diversity was greatest where bracken litter had been reduced, but species composition was also influenced by light sheep grazing. There was a significant loss of some chemical elements from bracken that could not be accounted for in other pools, and hence potentially lost from the system. In absolute terms large amounts of C and N were lost, but when expressed as a percentage of the total amount in the system, Mg was potentially more important with losses of almost a third of the Mg in the surface soil-vegetation system. There is, therefore, a potential dilemma between controlling a mid-successional invasive species for conservation policy objectives, especially when that species has evolved to sequester nutrients, and the negative effect of increasing environmental costs in terms of carbon accounting required, the potential input of nutrients to aquatic systems, and long-term nutrient loss. There is, therefore, a need to balance conservation goals against potential damage to biogeochemical structure and function.     

Techniques to Reduce the Impact of Asulam Drift from Helicopter Sprayers on Native Vegetation

Asulam is often applied from the air to control bracken. This herbicide affects other ferns and spray drift could affect their survival. This paper discusses the use of bioassays to assess drift (a) spatially around a single bracken patch, (b) downwind from sprayed areas, and (c) spatially in undulating terrain and with different vegetation cover types. The aims were to develop policies to protect sensitive habitats. It is suggested that “no-spray” buffer zones in excess of 160–180 m are needed to minimise risk. Protection of rare ferns from overstorey vegetation or from steep slopes did not occur. Although less drift was found upwind there was significant damage at the end of the helicopter runs because of errors in switching the sprayer on and off.     

Effects of herbicide spray drift on selected species of nature conservation interest: the effects of plant age and surrounding vegetation structure

There has been increasing awareness of the possible impact of herbicide drift on vegetation in nature reserves and field-margin habitats adjacent to treated areas. However, relatively little is known about the impact of such drift on species typical of these habitats. To investigate this problem a series of bioassay experiments simulating spray drift were carried out with five native plant species of different age placed at different distances up to 4 downwind from a sprayer under standardized conditions. These experiments used three herbicides--glyphosate, MCPA and mecoprop--in three types of surrounding vegetation structure--short, medium-height and tall grassland. Many plants showed symptoms of damage after spraying but showed no significant growth reduction at the end of the season even underneath the sprayer. Where a reduction in yield was found, it occurred close to the sprayer. In general, young plants were more often affected than old ones. Yield promotion occurred for some species between 2 and 4 m downwind of the sprayer (curvilinear response) with unknown ecological consequences. The structure of the surrounding vegetation influenced the response for some species, which indicates that deposition patterns can be complex, and thus there may be difficulty in predicting effects in semi-natural communities from simple deposition models.     

Assessment of the effects of herbicide spray drift on a range of plant species of conservation interest

With increasing use of herbicides there has been growing concern that spray drift from treated land will affect vegetation on adjacent nature reserves and other areas of high conservation interest. A preliminary attempt was made to assess this risk by placing a range of native plant species at different distances downwind from standardised drift events and assessing lethal effects and sublethal damage. Five herbicides were tested: asulam, 'Finesse' (chlorsulfuron + metsulfuron-methyl), glyphosate, MCPA and mecoprop. Applications were made at the appropriate time of years for each herbicide (autumn, spring and summer), and at both low and high wind speeds. The maximum safe distance at which no lethal effects were found was 6 m from the sprayer, but for most herbicides the distance was 2 m or less. Generally, damage symptoms were found at greater distances than lethal effects, but in most cases there was rapid recovery by the end of the growing season. These observations are consistent with drift-deposition models, in which the fallout of herbicide droplets has been measured. It is suggested that buffer zones surrounding nature reserves should be in the order of 5-10 m for ground sprayers to minimise the risk of herbicide impacts on these habitats.